1. Field of the Invention
The present invention relates to a polyolefin-based thermoplastic polymer composition, and more particularly to a polyolefin-based thermoplastic polymer composition having high surface polarity leading to excellent paint adhesion
2. Background of the Related Art
Generally, plastic parts, which are used as automotive interior and exterior parts, and parts of electric home appliances, are painted for improvements in aesthetic effects and surface properties, and for this, good adhesion between plastic resin and paints are required. Nonpolar polyolefin-based thermoplastic resins, such as polyethylene or polypropylene, are poor in adhesion with paints, and thus, have many difficulties in painting. To overcome such difficulties, various methods of surface pretreatment or methods of using functional additives are developed and being applied.
The surface pretreatment methods generally include a flame treatment method, a plasma treatment method, a UV irradiation method, a primer treatment method and a combination of two or more of these methods. However, the surface pretreatment methods have problems, such as additional equipment investment and increases in operation and maintenance costs. Particularly, the primer treatment method which is traditionally mainly used is a method of imparting paint adhesion to the surface of polyolefin-based thermoplastic resin by pre-applying chlorinated polyolefin-based resin to the polyolefin-based thermoplastic resin surface, and has problems in that it causes an increase in costs and uses environment-unfriendly materials.
The methods of using functional additives without surface pretreatment include a method of adding a large amount of polypropylene-g-maleic anhydride, a method of adding polyols having special chemical structures, and a method of chemically introducing functional additives into polyolefin. Among these methods, the method of adding a large amount of modified polyolefin, such as polypropylene-g-maleic anhydride, and the method of adding polyols having special chemical structures, have problems in that production cost is increased by the use of a large amount of expensive materials, and the physical properties of the resulting composite material are deteriorated by the addition of a large amount of additives. The method of chemically introducing functional additives into polyolefin (U.S. Pat. No. 6,133,374), which is a preparation method based on chemical decomposition, has a problem in that the control of chemical reaction is not easy, and thus, it is very difficult to obtain a polyolefin composite material with uniform and regular physical properties.
Korean patent Nos. 362824 and 395399 disclose methods of preparing polyolefin-based thermoplastic elastomers containing an acrylate-based copolymer. The thermoplastic elastomers prepared by these preparation methods are high in surface polarity and excellent in physical properties and chemical resistance, but very low in flowability. Thus, for the surface modification of the polyolefin-based composite material, a large amount of additives should be added to the polyolefin-based resin, resulting in deterioration in the physical properties and processability of the polyolefin composite material. For this reason, these methods were difficult to apply.